During any given cycle, three tags will predominantly be at play (using OpenBSD 5.5 as an example...):

OPENBSD_5_5_BASE -- The intent of this tag is to define all files used to create OpenBSD 5.5-release which also is the flavor (Flavors are further defined in Section 5.1 of the project's FAQ...) found on the official OpenBSD 5.5 CD set. Once files are tagged, no changes will be checked into this branch of the repository. Ideally, one could check out this branch, compile the base system, Xenocara, or ports from it today, next month, or next year, & get exactly the same binaries, libraries, manpages, + any & all collateral.

Patches may ultimately be made to 5.5-release, but they will not be checked into this CVS branch. Again, the point of this branch is to define what constituted the -release flavor of the operating system. Once -release is defined, it is not changed.

Note that the ports tree (see Section 15 of the FAQ for more details...) for -release also does not change after tagging has occurred.

OPENBSD_5_5 -- Patches eventually need to be made to most releases. Some number of files within -release will need to be modified. These changes will be checked into this branch only.

Checking out this CVS branch may not yield the same set of files today, next month, or next year. However, as outlined in Section 5.1 of the FAQ, OpenBSD 5.5 will cease to be supported as of the release of OpenBSD 5.7, so upon the release of that version, no further changes will be checked into the OPENBSD_5_5 branch.

Note that this CVS branch is synonymous for OpenBSD's -stable flavor. While users of -release may need to patch their systems with information found on the errata page, -stable users can simply update their local CVS repositories per the Following -stable page, & Section 5.3.3 of the FAQ, & rebuild the entire system.

Some security patches & a few updates will be made to the ports tree in this branch during the maintenance cycle for OpenBSD 5.5.

HEAD -- Active development for the next version of OpenBSD always occurs at the HEAD of the CVS repository. The flavor of OpenBSD generated from this branch is -current. Snapshots of the more popular platforms are generated nearly every day, & less so for the more exotic platforms.

Since this branch is where active development occurs, the files at HEAD are volatile. Coding errors may exist. Those who use snapshots of -current are expected to understand the potential instability of the system + ports, & possess some ability to deal with the changing landscape & potential loss of data. Shrew users of -currentshould be reading the Following -current page, Section 5.3 of the FAQ along with the project's misc@, ports@, & tech@ mailing lists for discussions of what is the current status of the -current flavor.

Note that files at the head of CVS can potentially be changed many times before tagging before the next release of OpenBSD is finalized.

Although the OPENBSD_5_5_BASE tag has been created in CVS, there are still some final changes being made before declaring 5.5 done to the world. While the chances for major source code changes is nearing zero at this time, the developers are continuing to assess & test what they want to declare to be the final form of this version. As soon as they are comfortable with the status, 5.5 will be declared done, & development will immediately start on future versions, focusing most on what will be in OpenBSD 5.6.